We develop the Automatic Process Control system to maximize the number of available process chambers by controlling the time to start cleaning each chamber. Firstly, to achieve the purpose we build the controller model which creates and changes the pseudo RPSC counter properly by controlling other factors: unit priority, robot sequence etc. Secondly, for testing the control system we design one of the representative PECVD systems, and experiment the simulated system with the APC system and without it under various conditions. Finally, we optimize the system with the Evolution Strategy. As a result, not only major performance indicators; cycle time and throughput but also the variations of them have improved than before adapting the system. The contribution of this research is to present the practical solution concerned with various and complex issues in the real world.